Brake



April 25, 1933. I H. F. PARKER BRAKE Filed May 1'7, 1330 a m M INVENTOR. HUMPHREY F. PARKER ATTORNEY Patented Apr. 25, 1933 p UNITED STATES PATENT OFFICE HUMIH REY F. PARKER, OF SOUTH BEND, INDIANA, ASSIGNOR TO BENDIX BRAKE COMPANY, OF SOUTH BEND, INDIANA, A CORPORATION OF ILLINOIS BRAKE Application filed May 17,

This invention relates to brakes and more particularly toi'nternal expanding brakes.

An object of the invention is the provision of a brake designed to obtain an increase in the applied pressure. I

Another object of the invention is the provision of a brake in which the braking efl'ect varies directly as the coefiicient of friction.

Another object of the invention is the provision of a brake having means for transmittin tangential force to the brake from the bra ing elements.

Another object of the invention is the provision of a brake having means for applying the braking elements with pressure at the centers of the respective braking elements:

A further object of the invention is to provide a brake in which multiplication of the applied pressure is obtained.

The above and other objects of the invention including various desirable details of construction will be apparent from the following description of the illustrative embodiment, shown in the accompanying drawing, in which:

Figure 1 is a side elevation of a brake embodylng the invention;

Figure 2 is a sectional view substantially on line 2-2, Figure 1;

Figure 3 is a sectional view substantially on line 33, Figure 1; and

Figure at is a sectional view substantially on line 4 -4, Figure 1.

In the embodiment illustrated, there is provided, a conventional rotatable drum 10 at the open side of which is a stationary support such as a backing plate 11. Arranged within the drum on the backing plate 11 are suitable anchors 12 and 13 on which are movably positioned a primary shoe 14 and a secondary shoe 15. The anchors serve to positively guide the shoes in a radial direction.

The shoes are of a conventional type comprising a rim 16, a web 17 supporting the rim and a suitable lining 18 secured to the rim and adapted for co-operation with the drum. The shoes are connected at their respective ends by return springs 19 and 20 which maintain the shoes against suitable stops 21 and 22 when the brake is in the off position. The

1930. Serial No. 453,381.

shoes are arranged in anoppositely disposed position and each covers roughly 120 deg. of the circumference of the drum.

Positioned'on the backing plate adjacent the anchors 12 and 13 are suitable posts or studs 23 and 24. These studs extend upwardly through openings in the webs 17 and pivotally mounted upon the posts are cams 25 having two lobes 26 and 27 and an arm 28.

Positioned in one of the gaps between the primary and secondary shoes is an actuating shoe 29 comprising a rim 30 on which is suitably secured a lining 31, and a web 32 supporting the rim. The web is connected atits respective ends by suitable links 33 and 34 to the arms 28 on the cams 25.

The actuating shoe is operated by a cam 35 engaging the rim 30, the cam being formed or suitably secured to a shaft 36 positioned for rotation on the backing plate, and con-' necting the actuating shoe to a suitable fixed support 38 are return springs 37.

In operation, the actuating shoe is forced against the brake drum by the cam 35 operated through suitable linkageconnected to a brake pedal, not shown. Upon engagement of the actuating shoe with the brake drum,

a slight circumferential movement is impartled thereto and this movement forces the cams 25 against the primary and secondary shoes or main shoes.

It is to be observed that the cam 25, because of the relative position of the lobes, is a double action cam, hence the shoes may be operated in both the forward and reverse direction. It therefore, follows that the forward and reverse braking effects are equal. This is a much desired result.

It will also be observed that the tangential forces on the primary and secondary shoes or main shoes are transmitted to the anchor pins located near their centers, that the cams are positioned on the backin plate and that the distance from the cam aces to the anchor pins is less than that from the actuating shoe tip to the anchor pins. It will, therefore, be apparent that by applying pressure to the main shoes at their centers and in transmitting the resultant tangential force due to the wiping action of the drum to the anchor pins,

the braking efl'ect varies direct-ly'as the coeflicient of friction,

While the preferred embodiment of the invention has been described, it is to be understood that this is given merely as an example of the underlying principals ofthe invention and since this may be incorporated in other specific mechanical structures, 1 do not in tendlto be limited to those shown, except as such limitations are clearly imposed bythe appended claim.

Having thus described the various features of the invention, what I claim is new 'and'desire to secure by Letters Patent is:

A brake comprising a rotatable drum, a

fixed support associated with the drum, centrally anchored primary and secondary shoes arranged in oppositely disposed relation on the support and adaptable for movement thereon, double action cams positioned on the support and adaptable for applying forces at substantially the center of the respective shoes, an actuating shoe positioned between the primary and secondary shoes adapted to be moved against the drum and to be given a slight circumferential movement thereby and means connecting the actuating shoe with the'cams so that the cams may be actuated to apply the primary and secondary shoes in either a forward or reverse direction with equal braking efiects.

In testimony whereof, I have hereunto si ed m name. I

y HREY F.. PARKER. 

